EP2698507B1 - System and method for temperature control of reheated steam - Google Patents
System and method for temperature control of reheated steam Download PDFInfo
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- EP2698507B1 EP2698507B1 EP12180786.1A EP12180786A EP2698507B1 EP 2698507 B1 EP2698507 B1 EP 2698507B1 EP 12180786 A EP12180786 A EP 12180786A EP 2698507 B1 EP2698507 B1 EP 2698507B1
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- Prior art keywords
- steam
- turbine
- temperature
- reheater
- inlet
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
- F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
- F01K7/22—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines having inter-stage steam heating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
- F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
- F01K7/22—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines having inter-stage steam heating
- F01K7/226—Inter-stage steam injection
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
- F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
- F01K7/22—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines having inter-stage steam heating
- F01K7/24—Control or safety means specially adapted therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22G—SUPERHEATING OF STEAM
- F22G5/00—Controlling superheat temperature
- F22G5/12—Controlling superheat temperature by attemperating the superheated steam, e.g. by injected water sprays
- F22G5/14—Controlling superheat temperature by attemperating the superheated steam, e.g. by injected water sprays by live steam
Definitions
- This invention relates generally to a temperature control system and a method for controlling the outlet temperature of a reheater, particularly at low turbine load.
- a modern steam generator can include a complex configuration of various thermal and hydraulic units for preheating and evaporating water, and for superheating steam.
- the surfaces of such units are arranged to facilitate: a complete and efficient fuel combustion while minimizing emissions of particulate and gaseous pollutants; steam generation at a desired pressure, temperature and flow rate; and to maximize recovery of the heat produced upon combustion of the fuel.
- reheaters and superheaters are specially designed tube bundles capable of increasing the temperature of saturated steam. Additionally, reheaters and superheaters are designed to obtain specific steam outlet temperatures, while keeping metal temperatures from becoming too elevated, and limiting steam flow pressure losses.
- a reheater or a superheater is a single-phase heat exchanger comprising tubes through which steam flows, and across which the combustion or flue gas passes on the outside of the tubes. Reheater and superheater tube bundles are often made of a steel alloy capable of withstanding high operating temperatures.
- the reheater typically provides the steam for a second turbine following the first turbine, which is typically fed directly from the feed water cycle going through the steam generator.
- the first turbine is typically known as high-pressure or HP turbine and the second turbine or turbine group as intermediate pressure or IP turbine or turbine group.
- the reheater receives its feed stream from the steam which exits the HP turbine.
- reheater outlet temperature (RHO) required at main continuous rated (MCR) conditions may not be achieved at certain load levels. As a consequence the IP turbine will not receive steam heated to the optimal operational temperature.
- a known method to control reheat steam temperature is by water spray, also called direct contact attemperation or de-superheating, by which a cooling water spray is added to the fluid entering the reheater.
- This method can have a negative effect on cycle efficiency.
- Another method is to use excess air supplied to the boiler for reheater steam temperature control. This method can have a negative effect on boiler efficiency.
- Other solutions include drawing off steam from the super heater and/or reheater, leaving however the problem of finding a disposal path for the extracted steam. The methods described above can only be applied if the steam is too hot.
- German patent number 821 790C discusses the use of tandem high pressure steam turbine bypasses to maintaining and control the inlet temperature of a second turbine of two steam turbines arranged in a series.
- the bypasses are connected branch from the main steam line downstream of the steam generator.
- German patent number DE 31 49 772 A1 further discusses thd a method for controlling the temperature of desuperheated steam in a turbine bypass.
- the method includes redundant temperatures sensors in the bypass line downstream of desuperheating water sprays that measure the actual steam temperature after the desuperheating.
- a temperature control system with all features of appended independent claim 1, inter alia including a by-pass line with a by-pass control valve branching off a live steam circuit to a first turbine in a sequence of at least two turbines, with a steam exit line of the first turbine merging with the by-pass line into the inlet of a reheater heated by a steam generator and connected to a second turbine of the sequence of at least two turbines, and having a steam mixing chamber at or after the point of merging and before the inlet into the reheater.
- the steam mixing chamber has preferable a first inlet connected to the by-pass line and a second inlet connected to the steam exit line of the first turbine.
- the steam mixing chamber includes preferably a static steam mixer.
- the line to the by-pass can be preferably connected to a location within the steam generator downstream the primary superheater, e.g. as intermediate boiler extraction.
- a method for controlling the outlet temperature of a reheater positioned in the steam path between a first turbine and a second turbine in a sequence of at least two turbines wherein at low unit loads the steam temperature at the inlet to the reheater is raised at a pressure lower than the main continuous rated operation pressure by extracting steam from a live steam line connecting the steam generator with the first turbine at a point within the steam, as specified in detail by appended independent claim 4, and mixing the extracted steam with the steam from the first turbine such that the inlet steam temperature to the reheater is raised to a temperature sufficient to maintain the outlet temperature at the desired level, e.g. close to the MCR temperature or closer to the HP turbine/live steam temperature.
- Fig. 1 shows a schematic diagram of a section of a steam power plant designed to provide power to a public power grid.
- the steam is generated in a boiler 10.
- the boiler 10 receives water from condenser (not shown) or a source external to the plant.
- the water passes through a feed water preheater 11 as shown before entering the boiler.
- the boiler 10 can be fired directly by fossil fuels such as coal or gas or by a non-convention heat source in form of a secondary heat exchange cycle or as is otherwise known in the industry.
- the live steam is generated within a cascade of heat exchangers 12 before exiting the boiler into the main/live steam pipework 13.
- the feed pipe 13 directs the steam into the inlet of a first turbine 14, which is in this example a high-pressure (HP) turbine within several turbine stages of.
- the main steam control valve 131 controls the amount of steam entering the HP turbine 14.
- the partially expanded steam is returned in the cold reheat (CRH) line 15 to the inlet of a reheater section 16 of the boiler.
- CSH cold reheat
- the partially expanded steam is reheated using the heat generated in the boiler 10.
- the reheat outlet (RHO) is connected through the hot reheater (HRH) line 17 with the inlet of a second turbine 18, which is in this example an intermediate-pressure (IP) turbine within several turbine stages.
- IP intermediate-pressure
- the turbines share a single rotor 19 which drives a generator (not shown).
- Further turbine stages may include additional IP turbines or one or more low pressure (LP) turbines with or without additional reheating circuits.
- the principles of the present invention can be applied to any steam power plant with a reheating system and at least two turbines connected through a reheating system.
- the system of FIG. 1 further includes a by-pass line 132 connecting the main steam line 13 with the CRH line 15.
- the amount of live steam taken from the main line is controlled by a by-pass valve 133.
- a spray cooler 134 is installed at the outlet of the HP by-pass valve to control the temperature T2 in the HP by-pass exhaust line.
- the by-pass line directs steam into a mixing chamber 151 within the CRH line 15.
- the second inlet to the mixing chamber 151 is connected to the exit of the HP turbine 14. From the mixing chamber 151 the CRH line 15 connects to the inlet of the reheater 16.
- the mixing chamber 151 of this example is a static mixer with fixed elements made of steel or steel alloy suitable for the steam temperature required for this application.
- Such mixers are commercially available for example as STATIFLOTM series 800/850.
- HP bypass system During operation in a conventional power plant with a by-pass the HP bypass system has the following standard functions according to the standard ANSI/ISA-77.13,01-1999:
- the by-pass line 132 typically includes a de-superheater 134, which can be a spray cooling chamber located within or after the by-pass valve 133.
- reheater outlet (RHO) steam temperature T4 In contrast to known applications for reheat temperature control, it is the aim of the present example to raise the inlet temperature T3 of the steam to the reheater section 16, which will, assuming a constant or similar heat input into the boiler, result in an increased reheater outlet (RHO) steam temperature T4.
- the HP bypass valve 133 is operated in a way to control the RHO temperature T4 by means of by-passing live steam around the HP turbine 14 directly into the cold reheat (CRH) line 15.
- the pressure of the live steam is reduced to the pressure of the cold reheat (CRH) steam. This leads to a temperature reduction of the life steam by throttling (Joule-Thompson-Effect).
- the steam downstream the HP by-pass valve 133 has a temperature T2 higher than the temperature T1 of CRH steam coming from the HP turbine exhaust.
- T2 the temperature of CRH steam coming from the HP turbine exhaust.
- the by-pass line 132 extracts steam from an intermediate point in the superheater section 12, which is located after the steam/water separator 121.
- the live steam temperature T5 may be increased.
- the temperature T2 after the throttling will however be lower as the steam temperature T6, this is again due to the Joule-Thompson rule.
- the above basic steps to increase the temperature can be refined to match any existing design parameters of the power plant.
- the reduction of pressure in the HP by-pass valve 132 can be adjusted to maximum the pressure of the cold reheat (CRH) steam design values.
- the temperature T2 of the by-pass steam can be reduced by suitable cooling such as spray water cooling in the de-superheater 134.
- suitable cooling such as spray water cooling in the de-superheater 134.
- the mixing can take place in the standard CRH piping 15.
- the by-pass mass flow required to achieve a high CRH inlet temperature T3 may be larger than in the first example above. But the loss of efficiency can be offset by the reduced costs in implementing this variant of the invention.
- This kind of operation reduces the mass flow through the HP turbine more than the solution without using spraywater. As a large amount of spray water is required, the mass flow to the second turbine is much greater than when not using spray water.
- the hot reheater outlet temperature (HRH temperature) T4 is controlled by adjusting the cold reheater inlet temperature (CRH temperature) T3.
- the CRH temperature T3 is set such that a desired HRH temperature can be obtained with the heat input from the boiler 10 into the reheater 16. This heat input can be calculated from the boiler and boiler fuel feed parameters.
- the CRH temperature after mixing the mass flow from the turbine 14 with the mass flow from the by-pass 132 can be adjusted by enthalpy balances over the HP 14 turbine and the HP by-pass valve 133.
- the enthalpy balance over the HP turbine yields temperature T1 at the exit of the HP turbine 14.
- an enthalpy balance over the HP by-pass 132 delivers the temperature T2 downstream the HP bypass valve.
- the mixing temperature T3 can then be calculated. If required, the HP by-pass valve exhaust temperature T2 can be adjusted by spraying water in the de-superheater 134.
- the pressure drop over the HP by-pass valve 133 is controlled in a similar way as the temperature,
- the pressure in the HP bypass exhaust line 132 must be slightly higher than the CRH pressure, to be sure that the HP by-pass exhaust steam can enter the CRH line 15.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Control Of Turbines (AREA)
Description
- This invention relates generally to a temperature control system and a method for controlling the outlet temperature of a reheater, particularly at low turbine load.
- As described for example in the United States patent no.
5,605,118 , a modern steam generator can include a complex configuration of various thermal and hydraulic units for preheating and evaporating water, and for superheating steam. The surfaces of such units are arranged to facilitate: a complete and efficient fuel combustion while minimizing emissions of particulate and gaseous pollutants; steam generation at a desired pressure, temperature and flow rate; and to maximize recovery of the heat produced upon combustion of the fuel. - As part of the modern steam generator, reheaters and superheaters are specially designed tube bundles capable of increasing the temperature of saturated steam. Additionally, reheaters and superheaters are designed to obtain specific steam outlet temperatures, while keeping metal temperatures from becoming too elevated, and limiting steam flow pressure losses. Essentially, a reheater or a superheater is a single-phase heat exchanger comprising tubes through which steam flows, and across which the combustion or flue gas passes on the outside of the tubes. Reheater and superheater tube bundles are often made of a steel alloy capable of withstanding high operating temperatures.
- The reheater typically provides the steam for a second turbine following the first turbine, which is typically fed directly from the feed water cycle going through the steam generator. Referring to the respective state of expansion, the first turbine is typically known as high-pressure or HP turbine and the second turbine or turbine group as intermediate pressure or IP turbine or turbine group. The reheater receives its feed stream from the steam which exits the HP turbine.
- It can be important for the heat rate and cycle efficiency of a steam generator, such as a carbonaceous fuel boiler-turbine power plant, to regulate and control reheater steam temperature within narrow limits. To maintain a constant temperature can be particularly challenging when a power plant operates at a low load, for example during start-up, as the pressure of the reheat section is also very low. Depending of the type of steam generator of boiler, the reheater outlet temperature (RHO) required at main continuous rated (MCR) conditions may not be achieved at certain load levels. As a consequence the IP turbine will not receive steam heated to the optimal operational temperature.
- A known method to control reheat steam temperature is by water spray, also called direct contact attemperation or de-superheating, by which a cooling water spray is added to the fluid entering the reheater. This method can have a negative effect on cycle efficiency. Another method is to use excess air supplied to the boiler for reheater steam temperature control. This method can have a negative effect on boiler efficiency. Other solutions include drawing off steam from the super heater and/or reheater, leaving however the problem of finding a disposal path for the extracted steam. The methods described above can only be applied if the steam is too hot.
- German patent number
821 790C discusses the use of tandem high pressure steam turbine bypasses to maintaining and control the inlet temperature of a second turbine of two steam turbines arranged in a series. The bypasses are connected branch from the main steam line downstream of the steam generator. - German patent number
DE 31 49 772 A1 further discusses thd a method for controlling the temperature of desuperheated steam in a turbine bypass. The method includes redundant temperatures sensors in the bypass line downstream of desuperheating water sprays that measure the actual steam temperature after the desuperheating. - In view of the prior art it is seen as an object of the present invention to provide more efficient means and methods for controlling the temperature of the reheater, particularly at low (i.e sub-operational) loads or pressure in the steam path.
- According to an aspect of the present invention, there is provided a temperature control system with all features of appended independent claim 1, inter alia including a by-pass line with a by-pass control valve branching off a live steam circuit to a first turbine in a sequence of at least two turbines, with a steam exit line of the first turbine merging with the by-pass line into the inlet of a reheater heated by a steam generator and connected to a second turbine of the sequence of at least two turbines, and having a steam mixing chamber at or after the point of merging and before the inlet into the reheater.
- The steam mixing chamber has preferable a first inlet connected to the by-pass line and a second inlet connected to the steam exit line of the first turbine. The steam mixing chamber includes preferably a static steam mixer.
- The line to the by-pass can be preferably connected to a location within the steam generator downstream the primary superheater, e.g. as intermediate boiler extraction.
- According to another aspect of the invention, there is provided a method for controlling the outlet temperature of a reheater positioned in the steam path between a first turbine and a second turbine in a sequence of at least two turbines, wherein at low unit loads the steam temperature at the inlet to the reheater is raised at a pressure lower than the main continuous rated operation pressure by extracting steam from a live steam line connecting the steam generator with the first turbine at a point within the steam, as specified in detail by appended independent claim 4, and mixing the extracted steam with the steam from the first turbine such that the inlet steam temperature to the reheater is raised to a temperature sufficient to maintain the outlet temperature at the desired level, e.g. close to the MCR temperature or closer to the HP turbine/live steam temperature. Hence it is a preferred object of the present invention to increase the reheater outlet temperature.
- The above and further aspects of the invention will be apparent from the following detailed description and drawings as listed below.
- Exemplary embodiments of the invention will now be described, with reference to the accompanying drawings, in which:
-
FIG. 1 is a schematic diagram of an exemplary embodiment in accordance with the invention ; and - Aspects and details of examples of the present invention are described in further details in the following description. Exemplary embodiments of the present invention are described with references to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the invention. However, the present invention may be practiced without these specific details, and is not limited to the exemplary embodiments disclosed herein
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Fig. 1 shows a schematic diagram of a section of a steam power plant designed to provide power to a public power grid. The steam is generated in aboiler 10. Theboiler 10 receives water from condenser (not shown) or a source external to the plant. The water passes through afeed water preheater 11 as shown before entering the boiler. Theboiler 10 can be fired directly by fossil fuels such as coal or gas or by a non-convention heat source in form of a secondary heat exchange cycle or as is otherwise known in the industry. - The live steam is generated within a cascade of
heat exchangers 12 before exiting the boiler into the main/live steam pipework 13. Thefeed pipe 13 directs the steam into the inlet of afirst turbine 14, which is in this example a high-pressure (HP) turbine within several turbine stages of. The mainsteam control valve 131 controls the amount of steam entering the HPturbine 14. At the exit of the HP turbine the partially expanded steam is returned in the cold reheat (CRH)line 15 to the inlet of areheater section 16 of the boiler. Within thereheater 16 the partially expanded steam is reheated using the heat generated in theboiler 10. - The reheat outlet (RHO) is connected through the hot reheater (HRH)
line 17 with the inlet of asecond turbine 18, which is in this example an intermediate-pressure (IP) turbine within several turbine stages. The turbines share asingle rotor 19 which drives a generator (not shown). Further turbine stages may include additional IP turbines or one or more low pressure (LP) turbines with or without additional reheating circuits. As will be however evident from the following description of examples, the principles of the present invention can be applied to any steam power plant with a reheating system and at least two turbines connected through a reheating system. - The system of
FIG. 1 further includes a by-pass line 132 connecting themain steam line 13 with theCRH line 15. The amount of live steam taken from the main line is controlled by a by-pass valve 133. Aspray cooler 134 is installed at the outlet of the HP by-pass valve to control the temperature T2 in the HP by-pass exhaust line. The by-pass line directs steam into amixing chamber 151 within theCRH line 15. The second inlet to themixing chamber 151 is connected to the exit of the HPturbine 14. From themixing chamber 151 the CRHline 15 connects to the inlet of thereheater 16. - The
mixing chamber 151 of this example is a static mixer with fixed elements made of steel or steel alloy suitable for the steam temperature required for this application. Such mixers are commercially available for example as STATIFLO™ series 800/850. - During operation in a conventional power plant with a by-pass the HP bypass system has the following standard functions according to the standard ANSI/ISA-77.13,01-1999:
- a) Control the pressure of the steam bypassing the HP turbine
- b) Control the pressure of the main steam from the boiler
- c) Control the flow and temperature of steam through the cold reheat line to cool the boiler reheater tubing
- d) Control the flow of steam through the main steam line to cool the boiler final superheater in case of sliding pressure operation
- e) Prevent lifting of main steam and hot reheat safety valves during transient operations
- f) act as safety valve for the superheater section of the boiler (TRD 421, DIN EN ISO 4126).
- To cool the boiler reheater tubing the by-
pass line 132 typically includes a de-superheater 134, which can be a spray cooling chamber located within or after the by-pass valve 133. - In contrast to known applications for reheat temperature control, it is the aim of the present example to raise the inlet temperature T3 of the steam to the
reheater section 16, which will, assuming a constant or similar heat input into the boiler, result in an increased reheater outlet (RHO) steam temperature T4. TheHP bypass valve 133 is operated in a way to control the RHO temperature T4 by means of by-passing live steam around theHP turbine 14 directly into the cold reheat (CRH)line 15. In the HP by-pass valve 133 the pressure of the live steam is reduced to the pressure of the cold reheat (CRH) steam. This leads to a temperature reduction of the life steam by throttling (Joule-Thompson-Effect). Depending on the live steam pressure, the temperature reduction can be in the range of for example 40 K. If, for example, reducing the live steam pressure and temperature by throttling from 100 bar overpressure and 540°C to 15 bar overpressure, the resulting steam temperature T2 after thebypass valve 132 is 500°C. If the maximum (= design) temperature of the CRH line is less than this temperature, the piping downstream of the HP bypass valve and even downstream of thesteam mixer 151 must be either exchanged for a high-temperature-resistant material before applying this example of the invention in plants already equipped with an HP turbine bypass. Another solution is to cool the steam further by spraywater injection in thespray cooler 134. - Depending on the design and operational parameters of the
bypass valve 133 the steam downstream the HP by-pass valve 133 has a temperature T2 higher than the temperature T1 of CRH steam coming from the HP turbine exhaust. By mixing the steam from the by-pass line 132 with the HP exhaust steam in theCRH line 15 the steam temperature T3 at the inlet of thereheater 16 is increased. In turn, the RHO steam temperature T4 can be maintained at the operational level for theIP turbine 18, even at low load. - It is further possible to extract the steam for the by-
pass line 132 from a location within theboiler 10 as shown inFIG. 1 . InFIG. 1 , the by-pass line 132 extracts steam from an intermediate point in thesuperheater section 12, which is located after the steam/water separator 121. By extracting the steam between the steam/water separator 121 and the boiler outlet of themain steam line 13, the live steam temperature T5 may be increased. The temperature T2 after the throttling will however be lower as the steam temperature T6, this is again due to the Joule-Thompson rule. - The above basic steps to increase the temperature can be refined to match any existing design parameters of the power plant. In case the plant allows for example for higher temperature in the by-pass line, the reduction of pressure in the HP by-
pass valve 132 can be adjusted to maximum the pressure of the cold reheat (CRH) steam design values. - If it is not feasible or desired by the power plant to use high-temperature-resistant material in the piping downstream of the by-
pass valve 132, the temperature T2 of the by-pass steam can be reduced by suitable cooling such as spray water cooling in the de-superheater 134. In this case, the mixing can take place in thestandard CRH piping 15. However the by-pass mass flow required to achieve a high CRH inlet temperature T3 may be larger than in the first example above. But the loss of efficiency can be offset by the reduced costs in implementing this variant of the invention. This kind of operation reduces the mass flow through the HP turbine more than the solution without using spraywater. As a large amount of spray water is required, the mass flow to the second turbine is much greater than when not using spray water. - In the above example, the hot reheater outlet temperature (HRH temperature) T4 is controlled by adjusting the cold reheater inlet temperature (CRH temperature) T3. The CRH temperature T3 is set such that a desired HRH temperature can be obtained with the heat input from the
boiler 10 into thereheater 16. This heat input can be calculated from the boiler and boiler fuel feed parameters. The CRH temperature after mixing the mass flow from theturbine 14 with the mass flow from the by-pass 132 can be adjusted by enthalpy balances over theHP 14 turbine and the HP by-pass valve 133. The enthalpy balance over the HP turbine yields temperature T1 at the exit of theHP turbine 14. Similarly, an enthalpy balance over the HP by-pass 132 delivers the temperature T2 downstream the HP bypass valve. The mixing temperature T3 can then be calculated. If required, the HP by-pass valve exhaust temperature T2 can be adjusted by spraying water in the de-superheater 134. - The pressure drop over the HP by-
pass valve 133 is controlled in a similar way as the temperature, The pressure in the HPbypass exhaust line 132 must be slightly higher than the CRH pressure, to be sure that the HP by-pass exhaust steam can enter theCRH line 15. - The present invention has been described above purely by way of example, and modifications can be made within the scope of the invention, particularly as relating to the way of measuring and calculating temperatures and enthalpy balances. The invention Z r is solely defined by appended independent claims.
-
-
boiler 10 - feed
water preheater 11 -
superheater section 12 - main/live steam line/
pipe 13 -
HP turbine valve 131 - by-
pass line 132 - by-
pass valve 133 - de-superheater 134
- first (HP)
turbine 14 - cold reheat (CRH)
line 15 - mixing
chamber 151 -
reheater 16 - Hot Reheat (HRH)
line 17 - second (IP)
turbine 18 -
rotor 19 - cold reheat (CRH) steam temperature T1
- by-pass steam temperature T2
- reheater inlet temperature T3
- hot/outlet reheat (HRH) steam temperature T4
- main/live steam temperature T5
- steam temperature at the extraction point T6
Claims (7)
- A temperature control system including a by-pass line (132) with a by-pass control valve (133) branching off a live steam circuit (13) to a first steam turbine (14) in a sequence of at least two steam turbines, with a steam exit line (15) of the first turbine merging with the by-pass line (132) into the inlet of a reheater (16) heated by a steam generator (10) and connected to a second steam turbine (18) of the sequence of at least two steam turbines, and having a steam mixing chamber (151) at or after the point of merging and before the inlet into the reheater (16), characterized in that the by-pass line (132) is connected to an intermediate point in a superheater section (12) of the steam generator (10), which is located after a steam/water separator (121).
- The control system of claim 1 wherein the steam mixing chamber (151) has a first inlet connected to the by-pass line (132) and a second inlet connected to the steam exit line (15) of the first steam turbine (14).
- The control system of claim 1 wherein the steam mixing chamber (151) includes a static mixer.
- A method for controlling the outlet temperature of a reheater (T4) positioned in the steam path between a first turbine (14) and a second turbine (18) in a sequence of at least two steam turbines, wherein the steam temperature at the inlet to the reheater (T3) is raised by extracting steam from a live steam line (13) connecting the steam generator with the first turbine (14) from an intermediate point in the superheater section (12) of the steam generator (10), which is located after a steam/water separator (121), and mixing the extracted and expanded steam with the steam from the outlet of the first turbine (14) such that the inlet steam temperature to the reheater (T3) is raised to a temperature sufficient to maintain the outlet temperature (T4) at the desired level.
- The method of claim 4 wherein under low load conditions the desired level the outlet temperature (T4) is maintained equal or close to the outlet temperature (T4) at normal operating conditions.
- The method of claim 4 wherein the steam mass flow through the by-pass line (132) and/or through the first turbine (14) is controlled in response to the inlet steam temperature for the reheater (T3).
- The method of claim 4 wherein the steam mass flow through the by-pass line (132) and/or through the first turbine (14) is controlled in response to the outlet steam temperature for the reheater (T3).
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP12180786.1A EP2698507B1 (en) | 2012-08-17 | 2012-08-17 | System and method for temperature control of reheated steam |
PCT/EP2013/066929 WO2014026995A2 (en) | 2012-08-17 | 2013-08-13 | System and method for temperature control of reheated steam |
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EP12180786.1A EP2698507B1 (en) | 2012-08-17 | 2012-08-17 | System and method for temperature control of reheated steam |
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EP2698507A1 EP2698507A1 (en) | 2014-02-19 |
EP2698507B1 true EP2698507B1 (en) | 2017-03-01 |
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WO (1) | WO2014026995A2 (en) |
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CN103925021B (en) * | 2014-04-15 | 2016-02-17 | 上海平安高压调节阀门有限公司 | System of high and low pressure bypasses |
JP6615358B2 (en) | 2015-12-22 | 2019-12-04 | シーメンス エナジー インコーポレイテッド | Chimney energy control in combined cycle power plants. |
CN105781630A (en) * | 2016-03-02 | 2016-07-20 | 王欣 | Bypass control system of electric power generation steam turbine |
JP6899207B2 (en) * | 2016-10-11 | 2021-07-07 | 住友重機械工業株式会社 | Boiler system |
CN108836110B (en) * | 2018-08-18 | 2021-01-15 | 吴联凯 | Steam generator based on temperature measuring device and control method thereof |
CN110529210B (en) * | 2019-09-11 | 2024-05-03 | 东方电气集团东方锅炉股份有限公司 | Method and system for reheating heat supply steam extraction |
CN114635766B (en) * | 2022-01-06 | 2024-02-09 | 国核电力规划设计研究院有限公司 | Valve setting and controlling system and method for heat supply steam extraction pipeline of pressurized water reactor nuclear power unit |
BE1030715B1 (en) * | 2022-07-13 | 2024-02-12 | Keppel Seghers Belgium Nv | Method for generating steam in combination with an energy generation process as well as installation for this |
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DE821790C (en) * | 1950-08-17 | 1951-11-19 | Borsig A G | Device for temperature and volume control of steam turbines with reheating |
US4372125A (en) * | 1980-12-22 | 1983-02-08 | General Electric Company | Turbine bypass desuperheater control system |
JPS5810104A (en) * | 1981-07-10 | 1983-01-20 | Hitachi Ltd | Turbine plant and control thereof |
US4455836A (en) * | 1981-09-25 | 1984-06-26 | Westinghouse Electric Corp. | Turbine high pressure bypass temperature control system and method |
SU1554954A1 (en) * | 1988-06-02 | 1990-04-07 | Завод-Втуз При Производственном Объединении Турбостроения "Ленинградский Металлический Завод" | Apparatus for mixing gases |
US5605118A (en) | 1994-11-15 | 1997-02-25 | Tampella Power Corporation | Method and system for reheat temperature control |
JP2012135737A (en) * | 2010-12-27 | 2012-07-19 | Shimadzu Corp | Static mixing mechanism |
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2012
- 2012-08-17 EP EP12180786.1A patent/EP2698507B1/en not_active Not-in-force
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WO2014026995A3 (en) | 2014-08-07 |
WO2014026995A2 (en) | 2014-02-20 |
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